Effects of 17β-estradiol on adiponectin regulation of the expression of osteoprotegerin and receptor activator of nuclear factor-κB ligand

Associations between mixed urinary phenols and parabens metabolites and bone mineral density: Four statistical models

Phenols and parabens widely exist in personal care and consumer products and have been proved to be endocrine disrupting chemicals that could disturb bone metabolism. The current studies focusing on the associations between phenols and parabens with bone mineral density (BMD) drew contradictory conclusions. Considering the bias might be due to not considering the effects of mixed exposure, we conducted the first cross-sectional study to investigate the associations of both single and mixed metabolites of phenols and parabens with BMD in three populations by setting up four models: generalized linear regression model (GLM), weighted quantile sum (WQS) regression model, quantile g-computation (qgcomp) model and Bayesian kernel machine regression (BKMR) model, based on the US National Health and Nutrition Examination Survey (NHANES) database. We found that the association between the mixtures and total femur BMD in men was significantly negative. Bisphenol A (BPA) was shown to play the most important role in this negative association in the BKMR model, and this negative association was also confirmed in the GLM model with β coefficient (95% CI) being -0.02 (-0.04, -0.01). The relationships between the mixtures and femoral neck and trochanter BMD in postmenopausal women were significantly positive. Benzophenone-3 (BP-3) played the most significant role in the positive association with trochanter BMD, as confirmed by the WQS, qgcomp and BKMR models, and this positive association was also verified by the GLM model with β coefficient (95% CI) being 0.01 (0.00, 0.02). In conclusion, the association between the mixed phenols and parabens and BMD was negative in men while was positive in postmenopausal women, which was gender-specific. This study might provide new ideas for the prevention and treatment of osteoporosis and the control of personal care and consumer products containing phenols and parabens in the future.

Animal Models of Temporomandibular Joint Osteoarthritis: Classification and Selection

Temporomandibular joint osteoarthritis (TMJOA) is a common degenerative joint disease that can cause severe pain and dysfunction. It has a serious impact on the quality of lives of patients. Since mechanism underlying the pathogenesis of TMJOA is not fully understood, the development of effective tools for early diagnosis and disease-modifying therapies has been hindered. Animal models play a key role in understanding the pathological process of diseases and evaluating new therapeutic interventions. Although some similarities in disease processes between animals and humans are known, no one animal model is sufficient for studying all characteristics of TMJOA, as each model has different translatability to human clinical conditions. For the past 4 decades, TMJOA animal models have been studied by numerous researchers and can be broadly divided into induced, naturally occurring, and genetically modified models. The induced models can be divided into invasive models (intra-articular injection and surgical induction) or non-invasive models (mechanical loading, high-fat diet, and sleep deprivation). Different types of animal models simulate different pathological expressions of TMJOA and have their unique characteristics. Currently, mice, rats, and rabbits are commonly used in the study of TMJOA. This review sought to provide a general description of current experimental models of TMJOA and assist researchers in selecting the most appropriate models for different kinds of research.

Recombinant human insulin-like growth factor-1 promotes osteoclast formation and accelerates orthodontic tooth movement in rats

Background: IGF-1 may be an important factor in bone remodeling, but its mechanism of action on osteoclasts during orthodontic tooth movement is complex and unclear. Methodology: The closed-coil spring was placed between the left maxillary first molar and upper incisors with a force of 50 g to establish an orthodontic movement model. Eighty SD rats were randomized to receive phosphate buffer saline or 400 ng rhIGF-1 in the lateral buccal mucosa of the left maxillary first molar every two days. Tissue sections were stained for tartrate-resistant acidic phosphatase (TRAP), the number of TRAP-positive cells was estimated and tooth movement measured. Results: The rhIGF-1 group exhibited evidential bone resorption and lacuna appeared on the alveolar bone compared to the control group. Moreover, the number of osteoclasts in compression side of the periodontal ligament in the rhIGF-1 group peaked at day 4 (11.37±0.95 compared to 5.28±0.47 in the control group) after the orthodontic force was applied and was significantly higher than that of the control group (p<0.01). Furthermore, the distance of tooth movement in the rhIGF-1 group was significantly larger than that of the control group from day 4 to day 14 (p<0.01), suggesting that rhIGF-1 accelerated orthodontic tooth movement. Conclusion: Our study has showed that rhIGF-1 could stimulate the formation of osteoclasts in the periodontal ligament, and accelerate bone remodeling and orthodontic tooth movement.

Interstitial Leydig Cell Tumorigenesis-Leptin and Adiponectin Signaling in Relation to Aromatase Expression in the Human Testis

Although epidemiological studies from the last years report an increase in the incidences of Leydig cell tumors (previously thought to be a rare disease), the biochemical characteristics of that tumor important for understanding its etiology, diagnosis, and therapy still remains not completely characterized. Our prior studies reported G-protein coupled estrogen receptor signaling and estrogen level disturbances in Leydig cell tumors. In addition, we found that expressions of multi-level-acting lipid balance- and steroidogenesis–controlling proteins including peroxisome proliferator-activated receptor are altered in this tumor. In order to get deeper into the other molecular mechanisms that regulate lipid homeostasis in the Leydig cell tumor, here we investigate the presence and expression of newly-described hormones responsible for lipid homeostasis balancing (leptin and adiponectin), together with expression of estrogen synthase (aromatase). Samples of Leydig cell tumors (n = 20) were obtained from patients (31–45 years old) and used for light and transmission electron microscopic, western blotting, and immunohistochemical analyses. In addition, body mass index (BMI) was calculated. In tumor mass, abundant lipid accumulation in Leydig cells and various alterations of Leydig cell shape, as well as the presence of adipocyte-like cells, were observed. Marked lipid content and various lipid droplet size, especially in obese patients, may indicate alterations in lipid homeostasis, lipid processing, and steroidogenic organelle function in response to interstitial tissue pathological changes. We revealed significantly increased expression of leptin, adiponectin and their receptors, as well as aromatase in Leydig cell tumors in comparison to control. The majority of patients (n = 13) were overweight as indicated by their BMI. Moreover, a significant increase in expression of phospholipase C (PLC), and kinases Raf, ERK which are part of adipokine transductional pathways, was demonstrated. These data expand our previous findings suggesting that in human Leydig cell tumors, estrogen level and signaling, together with lipid status, are related to each other. Increased BMI may contribute to certain biochemical characteristics and function of the Leydig cell in infertile patients with a tumor. In addition, altered adipokine-estrogen microenvironment can have an effect on proliferation, growth, and metastasis of tumor cells. We report here various targets (receptors, enzymes, hormones) controlling lipid balance and estrogen action in Leydig cell tumors indicating their possible usefulness for diagnostics and therapy.

Tamoxifen Inhibits the Progression of Trauma-Induced Heterotopic Ossification in Mice

BACKGROUND Heterotopic ossification (HO) is a kind of abnormal mineralized bone which usually occurs in muscle, tendon, or ligament. There are currently no effective drugs for the treatment and prevention of HO. Developing effective drugs that can inhibit HO is of profound significance and would provide new strategies for clinical treatment of this disease. The present investigation evaluated the inhibitory effect of tamoxifen against HO. MATERIAL AND METHODS Using an Achilles tendon trauma-induced HO female mice model, we screened different doses of tamoxifen (1, 3, and 9 mg/kg) in mice to determine the optimal dosage on the inhibition of the HO formation. The curative effect of tamoxifen was also illustrated at different HO progression stages including inflammation, chondrogenesis, osteogenesis, and HO maturation. RESULTS Heterotopic bone was formed with typical endochondral ossification in Achilles tendons 6 weeks after surgery and continued to enlarge up to 12 weeks. The formation of HO was significantly inhibited with the treatment of tamoxifen at the dosage of 9 mg/kg, whereas 1 mg/kg and 3 mg/kg did not reduce HO bone volume remarkably. The progression of HO was both attenuated by tamoxifen from Day 1 and Week 4 post-surgery, whereas no inhibitory effect was shown at the osteogenesis and maturation stages treated with tamoxifen. CONCLUSIONS Tamoxifen exerts an inhibitory effect on the heterotopic bone progression at inflammation and chondrogenesis stages, with the TGF-ß signaling pathway suppressed following the increase in estrogen receptor alpha activity.

Circulatory pattern of cytokines, adipokines and bone markers in postmenopausal women with low BMD

Objective: In addition to some well-characterized bone turnover markers (BTMs), cytokines and adipokines have also been suggested to be linked to osteoporosis seen in menopause. However, there is much controversy on the possible association between these markers and bone mineral density (BMD). This study was aimed at measuring circulatory levels of selected cytokines, adipokines and BTMs in postmenopausal women with normal and low BMD. Methods: The study population included 71 post-menopausal women, of whom 25 had normal BMD, 31 had osteopenia and 13 had osteoporosis. Circulatory levels of selected pro-resorptive (TNF-α, IL-1β, IL-6, IL-8, IL-12, IL-17), anti-resorptive (IFN-γ, IL-4, IL-10, IL-13, TGF-β) and five adipokine markers (adiponectin, adipsin, lipocalin-2/NGAL, PAI-1 and resistin) were measured using the Multiplex system and read on the Magpix ELISA platform. Further, two bone turnover markers (PINP, CTX) as well as estradiol levels were assayed from the same samples. Results: While circulatory levels of cytokines were comparable between groups, women with low BMD had statistically significantly higher median circulatory levels of adipokines as compared to those with normal BMD. Further, while levels of CTX were not different between the two groups; PINP, PINP/CTX ratio and estradiol levels were significantly lower in women with low BMD. Levels of adiponectin, PINP, PINP/CTX ratio and estradiol correlated significantly with BMD of the hip and spine. Conclusion: The associations between various markers and BMD are complex and multivariate. Our data provide insights into the possible use of circulatory levels of cytokines, adipokines and bone turnover markers on the pathogenesis of postmenopausal osteoporosis because of the well-documented effects of these molecules on bone tissue and their relevance to osteoporosis.

Estrogen reverses nicotine-induced inflammation in chondrocytes via reducing the degradation of ECM

PROBLEM

Osteoarthritis (OA) is a chronic disease with a very high incidence and the pathology of which is quite complex. Epidemiological investigation showed that OA may be related to smoking and estrogen levels, but there are few studies focused on the cross-effect of these two factors. This research aims to investigate the molecular mechanism of nicotine and estrogen effects on chondrocytes to study the effect of smoking on the incidence of osteoarthritis in women.

METHOD OF THE STUDY

Nicotine was added to obtain inflammatory supernatants of macrophages, which were used to induce chondrocyte inflammation. Toluidine staining and immunohistochemistry were used to detect the extracellular matrix (ECM) of chondrocytes, while the important proteins in the metabolism of chondrocytes were detected by Western blot.

RESULTS

Nicotine-induced inflammatory supernatant promoted the degradation of ECM, such as type II collagen, aggrecan and proteoglycan 4. While in the presence of physiological concentrations of estrogen, this destructive effect is reversed. On the molecular level, estrogen (17β-estradiol, 1 nmol/L) can inhibit the matrix degrading enzymes and promote the transforming growth factor (TGF)-β1 pathway which is involved in matrix synthesis. However, in the presence of inflammatory induction, although estrogen could still inhibit the expression of matrix degrading enzymes, it inhibited the TGF-β1 pathway. Moreover, the different inflammatory factors in the inflammatory supernatant, mainly tumor necrosis factor-α, interleukin-1β, had different effects on the metabolic processes of chondrocytes.

CONCLUSION

Estrogen reverses nicotine-induced inflammation mainly via reducing the degradation of ECM. The cross-effect of estrogen and inflammatory factor inhibitors can be a potential clinical reference for OA patients.

Effects of RANKL Knockdown by Virus-like Particle-Mediated RNAi in a Rat Model of Osteoporosis

Rebalancing of the RANKL/OPG system seems to be an effective treatment strategy in postmenopausal osteoporosis. Here, we evaluate the knockdown of RANKL by in-vivo-delivered siRNA in a rat model of osteoporosis. Virus-like-particles (VLPs) derived from polyoma JC virus were used for delivering RANKL siRNA in ovariectomized (OVX) rats. 48 rats were ovariectomized and treated with either 17β-estradiol (E2), VLPs containing RANKL siRNA (siRANKL), or VLPs containing non-cognate siRNA (siCtrl). All OVX groups were subdivided into the prophylaxis group (PG) and the therapy group (TG). The PG received treatment directly after being OVX for 10 weeks. The TG received treatment 5 weeks after being OVX for 5 weeks. Rats were sacrificed 10 weeks after being OVX. Bone and blood samples were analyzed. E2 and siRANKL showed a significant knockdown of RANKL mRNA. A protein knockdown was observed with E2 and siRANKL in the TG but not in the PG. No distinct improvements in biomechanical and morphological properties of the bones were observed after siRANKL treatment. In the PG, E2 protected the bone structure. We demonstrated successful mRNA and protein knockdown by VLP-mediated RNAi in vivo. Knockdown of membranous RANKL did not result in significant improvements of bone properties in this model of early-stage postmenopausal osteoporosis.

Adiponectin signaling and its role in bone metabolism

Adiponectin, the most prevalent adipo-cytokine in plasma plays critical metabolic and anti-inflammatory roles is fast emerging as an important molecular target for the treatment of metabolic disorders. Adiponectin action is critical in multiple organs including cardio-vascular system, muscle, liver, adipose tissue, brain and bone. Adiponectin signaling in bone has been a topic of active investigation lately. Human association studies and multiple mice models of gene deletion/modification failed to define a clear cause and effect of adiponectin signaling in bone. The most plausible reason could be the multimeric forms of adiponectin that display differential binding to receptors (adipoR1 and adipoR2) with cell-specific receptor variants in bone. Discovery of small molecule agonist of adipoR1 suggested a salutary role of this receptor in bone metabolism. The downstream signaling of adipoR1 in osteoblasts involves stimulation of oxidative phosphorylation leading to increased differentiation via the likely suppression of wnt inhibitor, sclerostin. On the other hand, the inflammation modulatory effect of adiponectin signaling suppresses the RANKL (receptor activator of nuclear factor κ-B ligand) - to - OPG (osteprotegerin) ratio in osteoblasts leading to the suppression of osteoclastogenic response. This review will discuss the adiponectin signaling and its role in skeletal homeostasis and critically assess whether adipoR1 could be a therapeutic target for the treatment of metabolic bone diseases.

Relationships between serum Omentin-1 levels and bone mineral density in older men with osteoporosis

OBJECTIVE

To investigate the correlation between serum Omentin-1 levels and the presence of osteoporosis in older men.

METHODS

Serum Omentin-1, bone turnover biochemical markers, and bone mineral density (BMD) were determined in 45 older men with osteoporosis or 45 older men without osteoporosis (65-70 years old).

RESULTS

Omentin-1 levels were increased in older men with osteoporosis, and the differences remained significant after controlling for fat mass. Omentin-1 was negatively correlated with BMD. In a multiple linear stepwise regression analysis, Omentin-1, lean mass, but not fat mass, were independent predictors of BMD for the combined group. Significant negative correlations between Omentin-1 and bone-specific alkaline phosphatase (BAP) and bone cross-linked N-telopeptides of type Ⅰ collagen (NTX) were found. Omentin-1 was also independently associated with BMD and bone turnover markers in older men with osteoporosis and control groups that were considered separately.

CONCLUSIONS

Omentin-1 is an independent predictor of BMD in older men with osteoporosis, and it is negatively correlated with bone turnover biochemical markers. It is suggested that Omentin-1 may exert a negative effect on bone mass through the regulation of the osteoblast differentiation in the older men with osteoporosis.

Nonalcoholic fatty liver disease and decreased bone mineral density: is there a link?

PURPOSE

Liver diseases are associated with decreased bone mineral density (BMD) and evidence suggests that nonalcoholic fatty liver disease (NAFLD) affects several extra-hepatic organs, interacting with the regulation of multiple endocrine and metabolic pathways. This review focuses on the rapidly expanding body of evidence that supports a strong association between NAFLD and the risk of decreased BMD, expression of low bone mass (osteoporosis), or reduced mineralization (osteomalacia).

METHODS

We identified studies by searching PubMed for original articles published in English through March 2015 using the keywords "nonalcoholic fatty liver disease" or "fatty liver" combined with "bone mineral density", "osteoporosis", or "osteomalacia".

RESULTS

Recent cross-sectional and case-control studies involving both adults and children have consistently shown that patients with NAFLD exhibit a greater prevalence of decreased BMD compared with age-, sex-, and body mass index-matched healthy controls. Accumulating clinical and experimental evidence suggests that NAFLD may contribute to the pathophysiology of low BMD, possibly through the direct contribution of NAFLD to whole-body and hepatic insulin resistance and/or the systemic release of multiple pro-inflammatory, pro-coagulant, and pro-fibrogenic mediators.

CONCLUSIONS

Although more research is needed before firm conclusions can be drawn, it appears that there is a non-chance, statistical association between NAFLD and low BMD. This finding argues for more careful monitoring and evaluation of BMD among patients with NAFLD. The potential contribution of NAFLD itself to the development and progression of decreased BMD warrants further study.

Adiponectin exerts its negative effect on bone metabolism via OPG/RANKL pathway: an in vivo study

To explore the effects of adiponectin on the bone metabolism in vivo. Bone mineral density (BMD), bone microstructure, serum adiponectin levels, and biochemical markers of the bone turnover were measured in 12-week-old male Adipo-/- and WT mice. In addition, the osteoclast formation, osteoprotegerin (OPG), and the receptor activator of nuclear factor-κB ligand (RANKL) expression were examined. The serum adiponectin levels were normal in the WT mice while undetectable in the Adipo-/- mice. Compared with the WT mice, the Adipo-/- mice had higher BMD, more trabecular bone, greater bone volume fraction, and trabecular thickness in the left femur. On the contrary, fewer osteoclasts were observed in the Adipo-/- mice when compared with the WT mice. Meanwhile, the Adipo-/- mice had a significantly decreased serum carboxyl-terminal telopeptide of type 1 collagen (CTX)/osteocalcin (OC) ratio. Interestingly, both the adiponectin and RANKL would cause a significant increase of CTX/OC ratio in the co-culture of the CD14+ peripheral blood mononuclear cells and the osteoblasts from Adipo-/- mice. Further, immunohistochemistry assays in tibias and both the RT-PCR and immunoblot analyses in the cultured osteoblasts showed the Adipo-/- mice expressed lower levels of RANKL but higher levels of OPG. Adiponectin had a negative effect on the bone metabolism, and this negative effect might be mediated, at least in part, by the OPG/RANKL pathway.

Relationships between serum omentin-1, body fat mass and bone mineral density in healthy Chinese male adults in Changsha area

PURPOSE

The present study is firstly designed to identify the relationship between serum omentin-1 concentration, body fat mass and bone mineral density in healthy Chinese male adults in Changsha city.

METHODS

A total of 219 (20-80 years old) healthy subjects were enrolled in this cross-sectional study. Serum omentin-1, adiponectin, leptin, resistin and bone turn over biochemical markers were measured with enzyme-linked immunosorbent assay. Bone mineral density (BMD) and fat body composition were determined using dual-energy-X-ray absorptiometry.

RESULTS

Serum omentin-1 levels in the overweight subjects were significantly lower than those of the subjects with normal weight (p < 0.05). Omentin-1 was negatively correlated with weight (r = -0.418), body mass index (BMI, r = -0.419), waist circumference (r = -0.402), waist-to-hip ratio (WHR, r = -0.355), fat body mass (FBM, r = -0.430), fat % (r = -0.408), trunk fat (-0.431). However, after controlling for age, BMI and FBM, no significant correlation was noticed between omentin-1 and BMD at different skeletal sites. Pearson's correlation coefficients and partial correlation coefficients after adjustment showed no significant correlations between omentin-1 and bone turn over biochemical markers, including bone-specific alkaline phosphatase and bone cross-linked N-terminal telopeptides of type I collagen. Multiple line stepwise regression analysis revealed that FBM, WHR, adiponectin were important variables affecting omentin-1. Moreover, lean tissue mass was the most important factor affecting BMD and explained 10.5-14.7 % of the variance. Omentin-1, leptin and resistin were not the predictors of BMD.

CONCLUSIONS

Serum omentin-1 was negatively correlated with FBM and BMI in healthy Chinese male adults, It was not significantly correlated with bone turnover biochemical markers. Omentin-1 may exert ambiguous effects on BMD, which maybe caused by the complex interactions among adipokines, hormonal activity, and body composition and bone metabolism.

Estradiol inhibits osteoblast apoptosis via promotion of autophagy through the ER-ERK-mTOR pathway

Estradiol could protect osteoblast against apoptosis, and apoptosis and autophagy were extensively and intimately connected. The aim of the present study was to test the hypothesis that autophagy was present in osteoblasts under serum deprivation and estrogen protected against osteoblast apoptosis via promotion of autophagy. MC3T3-E1 osteoblastic cells were cultured in a serum-free and phenol red-free minimal essential medium (α-MEM). Ultrastructural analysis, lysosomal activity assessment and monodansycadaverine (MDC) staining were employed to determine the presence of autophagy, and real time PCR was used to evaluate the expression of autophagic markers. Meanwhile, the osteoblasts were transferred in a serum-free and phenol red-free α-MEM containing either vehicle or estradiol. Apoptosis and autophagy was assessed by using the techniques of real-time PCR, Western blot, immunofluorescence assay, and flow cytometry. The possible pathway through which estrogen promoted autophagy in the serum-deprived osteoblasts was also investigated. Real-time PCR demonstrated the expression of LC3, beclin1 and ULK1 genes in osteoblasts under serum deprivation, and immunofluorescence assay verified high expression of proteins of these three autophagic bio-markers. Lysosomes and autolysosomes accumulated in the cytoplasm of osteoblasts were also detected under transmission electron microscopy, MDC staining and lysosomal activity assessment. Meanwhile, estradiol significantly decreased the expression of proteins of the bio-markers of apoptosis, and at the same time increased the expression of proteins of the bio-markers of autophagy in the serum-deprived osteoblasts. Furthermore, the estradiol-promoted autophagy in serum-deprived osteoblasts could be blocked by estrogen receptor (ER) antagonist (ICI 182780), and estradiol failed to rescue the cells pretreated with an inhibitor of vacuolar ATPase (bafilomycin A) from apoptosis. Serum deprivation resulted in apoptosis through activation of Caspase-3 and induced autophagy through inhibition of phospho-mammalian target of rapamycin (p-mTOR). Both 3-methyladenine (3MA) and U0126 led to increase of apoptosis in osteoblasts with serum deprivation. Estradiol failed to over-ride the inhibitory effect of 3MA on phosphorylation of AKT but directly led to dephosphorylation of mTOR and upregulation of LC3 protein expression. However, the estradiol-enhanced LC3 protein expression was significantly suppressed by U0126 through inhibition of phosphorylation of extracellular signal-regulated kinase (ERK). Estradiol rescued osteoblast apoptosis via promotion of autophagy through the ER-ERK-mTOR pathway.

Adiponectin as a biomarker of osteoporosis in postmenopausal women: controversies

The literature reports indicating a link between plasma levels of adiponectin and body fat, bone mineral density, sex hormones, and peri- and postmenopausal changes, draw attention to the possible use of adiponectin as an indicator of osteoporotic changes, suggesting that adiponectin may also modulate bone metabolism. In this study, we attempted to analyze the available in vitro and in vivo results which could verify this hypothesis. Although several studies have shown that adiponectin has an adverse effect on bone mass, mainly by intensifying resorption, this peptide has also been demonstrated to increase the proliferation and differentiation of osteoblasts, inhibit the activity of osteoclasts, and reduce bone resorption. There are still many ambiguities; for example, it can be assumed that concentrations of adiponectin in plasma do not satisfactorily reflect its production by adipose tissue, as well as conflicting in vitro and in vivo results. It seems that the potential benefit in the treatment of patients with osteoporosis associated with the pharmacological regulation of adiponectin is controversial.

Interactions among bone, liver, and adipose tissue predisposing to diabesity and fatty liver

Growing epidemiological evidence connects obesity and its complications, including metabolic syndrome, diabetes, and nonalcoholic fatty liver disease (NAFLD) to reduced bone health and osteoporosis. Parallel to human studies, experimental data disclosed a complex network of interaction among adipose tissue, the liver, and the bone, which reciprocally modulate the function of each other. The main mediators of such crosstalk include hormonal/cytokine signals from the bone (osteopontin, osteocalcin, and osteoprotegerin), the liver (fetuin-A), and adipose tissue [leptin, tumor necrosis factor-α (TNF-α), and adiponectin]. Dysregulation of this network promotes the development of diabesity, NAFLD, and osteoporosis. We will review recent advances in understanding the mechanisms of bone-liver-adipose tissue interaction predisposing to obesity, diabetes, NAFLD, and osteoporosis and their potential clinical implications.

The impact of estradiol and 1,25(OH)2D3 on metabolic syndrome in middle-aged Taiwanese males

In addition to adipocytokines, estradiol (E2) and vitamin D have been reported to affect insulin sensitivity, glucose homeostasis and body weight. However, studies about the impact of E2 and vitamin D on metabolic syndrome (MetS) are still limited. The aim of this study is to clarify the roles of circulating E2 and vitamin D on the risk of MetS in middle-aged Taiwanese males. A total of 655 male volunteers, including 243 subjects with MetS (mean age: 56.7±5.8 years) and 412 normal controls (mean age: 55.1±3.6 years), were evaluated. Subjects with MetS had significantly lower circulating E2, 1,25(OH)₂D₃, and adiponectin, and higher leptin than those without MetS (P<0.001 for all comparisons). E2 and 1,25(OH)₂D₃ were significantly associated with 4 individual components of MetS; more than adiponectin and leptin that were only associated with 3 individual components. In multivariate regression analysis, E2 (beta = −0.216, P<0.001) and 1,25(OH)₂D₃ (beta = 0.067, P = 0.045) were still significant predictors of MetS independent of adiponectin and leptin. Further large studies are needed to confirm our preliminary results and elucidate the possible mechanism.

Relationship between serum omentin-1 level and bone mineral density in girls with anorexia nervosa

BACKGROUND

Adolescents with anorexia nervosa (AN) have low bone mineral density (BMD). Omentin- 1, the main circulating adipocytokine, plays an important role in bone metabolism in healthy individuals. However, their association with bone metabolism in AN is unknown.

METHODS

Serum omentin-1, bone turnover biochemical markers, and BMD were determined in 26 girls with AN and 24 healthy girls (15-18 years old).

RESULTS

Omentin-1 levels increased in AN subjects, and the differences became greater after controlling for fat mass. Omentin-1 was negatively correlated with BMD. In the multiple linear stepwise regression analysis, omentin-1, body mass index and lean mass, but not fat mass, were independent predictors of BMD for the combined group. Significant negative correlations were found between omentin-1 and bone-specific alkaline phosphatase, bone cross-linked N-telopeptides of type I collagen. Omentin-1 was also independently associated with BMD and bone turnover markers in the AN and control groups considered separately.

CONCLUSIONS

Omentin-1 was an independent predictor of BMD in adolescents with AN, and negatively correlated with bone turnover markers. This suggested that omentin-1 may exert a negative effect on bone mass by inhibiting bone formation in girls with AN.